Reliable Seismic Structural Analysis Using Interval Ground Motion

Vol.2 No.1

Year : 2013

Issue : Mar-May

Title : Reliable Seismic Structural Analysis Using Interval Ground Motion

Author Name : Mehdi Modares, Adam Venezia

Synopsis :

Abstract: Seismic analysis is an essential procedure to design a structure subjected to ground motion. However, throughout conventional seismic analysis, the structure is subjected to a limited number of recorded earthquake excitations. Moreover, the presence of variations and uncertainties in the recorded excitations within a single, and among different earthquakes is not considered in current seismic analysis procedures. One methods of quantifying the impreciseness and uncertainty is the interval or unknown-but-bounded representation. In this work, a new computationally feasible method for seismic structural analysis with interval uncertainty in the response spectrum is developed, which is capable of obtaining the bounds on the structure’s dynamic response. Using this method, first, the response spectra from various recorded earthquakes are combined in order to construct an interval function referred to as an interval response spectrum. Then, the response spectrum analysis is performed using the developed interval response spectrum, and the bounds of the dynamic response of the structure are obtained. This computationally feasible method shows that calculating the bounds on the dynamic response does not require an iterative procedure such as Monte-Carlo simulation. Numerical example problems, which illustrate the developed algorithm, are presented, along with a comparison of solutions obtained by Monte-Carlo simulation.

Study Of Engineering Properties Of Recycled Concrete Aggregate Concrete

Vol.2 No.1

Year : 2013

Issue : Mar-May

Title : Study Of Engineering Properties Of Recycled Concrete Aggregate Concrete

Author Name : PRAMOD GUPTA, RITESH BHATIA

Synopsis :

A series of experiments were conducted on two grades of concrete namely M25 and M40 with three nominal replacement ratios of 0%, 25% and 50% using recycled concrete aggregates (RCA). The RCA concrete was obtained using a new mix design in which the residual mortar content of the recycled aggregates was considered as a part of sand in the new concrete. For the six mixes, tests were conducted to determine the engineering properties of the RCA concrete and the results were compared to that of the natural aggregate concrete. A total of 72 specimens were cast and tested. The tests conducted included Slump, Non-destructive testing, Compressive strength, Splitting tensile strength and Elastic modulus. Based on the investigations it was found out that the proposed method gave comparable results to that of the concrete made of natural aggregates. Compressive strength, UPV, Rebound Hammer and Elastic modulus values were established to be more than that of the natural aggregate concrete while Slump and Splitting tensile strength were lesser.

Experimental and Analytical Comparison of RC Beam Strengthened with GFRP Strip

Vol.2 No.1

Year : 2013

Issue : Mar-May

Title : Experimental and Analytical Comparison of RC Beam Strengthened with GFRP Strip

Author Name : Hanmant Jadhav, Sachin Matade

Synopsis :

This study presents experimental performance and modes of failure of reinforced concrete (RC) beam strengthened with externally (bottom side) bonded glass fiber reinforced polymer (GFRP) strip. Experimental results compared with presenting finite element modeling of R C beam using ANSYS software. The finite elements model uses a discrete approach to reinforced concrete and three dimensional layered elements to model the fiber reinforced polymer (FRP) composites. The comparison is made for load deflection curve at midspan and mode of failure. The result obtained from finite element analysis was calculated at same location as the experimental test of the beams and accuracy of was compared. The load–deflection curve from finite element analysis is good agreement with the experimental results.

Mechanics of reinforced flyash slopes: A qualitative review

Vol.2 No.1

Year : 2013

Issue : Mar-May

Title : Mechanics of reinforced flyash slopes: A qualitative review

Author Name : Harvinder Singh

Synopsis :

Flyash-a waste by product-is proving a versatile material for the geotechnical use despite its low shearing strength. Past research has demonstrated its potential use in construction of embankments/slopes, filling of low land area etc. It is, now, a well documented fact that use of reinforcing element(s) in flyash slopes and other applications proves beneficial in enhancing its load carrying capacity. In this article, it has been tried to present the mechanics behind this phenomenon and a set of forces working, silently, inside the reinforced flyash/soil mass/slopes that become responsible for strength enhancement of the system. It will help readers to visualise reinforced-flyash system in term of forces and develop simplified analytical expressions governing the behaviour of reinforced slopes.

Behaviour Of Waste Plastic Fibre Reinforced Concrete Produced By Conventional Aggregates And Recycled Aggregates Under Alkaline Environment - An Experimental Investigation

Vol.2 No.1

Year : 2013

Issue : Mar-May

Title : Behaviour Of Waste Plastic Fibre Reinforced Concrete Produced By Conventional Aggregates And Recycled Aggregates Under Alkaline Environment - An Experimental Investigation

Author Name : Prahallada M.C, Prakash K.B

Synopsis :

The addition of fibres into concrete has been found to improve several of its properties like tensile strength, cracking resistance, impact, wear and tear, ductility, fatigue resistance etc. Many types of fibres like steel fibres, carbon fibres, GI fibres, glass fibres, asbestos fibres etc. can be used in fibre reinforced concrete. Waste plastics can also be used as fibres. The disposal of waste plastic is resulting in environmental pollution. Plastic is a non-biodegradable material, and it neither decays nor degenerates in water or in soil. On the other hand it pollutes the water and soil. Plastic if burnt releases many toxic gases, which are very dangerous to health. Such plastics can be used in concrete in the form of fibres to impart some additional desirable qualities to the concrete. This paper presents the results of waste plastic fibre reinforced concrete (WPFRC) produced from recycled aggregates subjected to alkali attack. The different percentages waste plastic fibre used in the experimentation are 0%, 0.5% , 1%, 1.5%, 2%, 2.5% and 3% with an aspect ratio of 50.The results are compared with the waste plastic fibre reinforced concrete (WPFRC) produced from granite aggregates

Analysis Of Supplemental Dampers With Base Isolated RC Frame

Vol.1 No.4

Year : 2013

Issue : Dec-Feb

Title : Analysis Of Supplemental Dampers With Base Isolated RC Frame

Author Name : SETIA, Isha Verma

Synopsis :

In this paper a typical five-storied reinforced concrete plane frames with full isolation are analyzed, assuming two ground types namely rock and moderately soft soil. These two ground types are combined with fundamental vibration periods of 2, 3 and 4 seconds respectively in a high-risk seismic region with the overall isolation system. The isolation systems are made of in-parallel high-damping laminated-rubber bearings and supplemental viscous dampers. Real accelerograms at El Centro 1940 are considered and analysis is carried out with SAP 2000 Version 12 using time history analysis. It is concluded that a supplemental viscous damping at the base is appropriate for controlling the isolator displacement, so avoiding overly large isolators and it is found that displacement will reduce in both the soil conditions; also displacement is less for higher vibration period and a comparison is also made for a base isolated structure with and without supplemental damper.

Analysis Of Skew Deck Slab Bridge By Analytical Methods

Vol.1 No.4

Year : 2013

Issue : Dec-Feb

Title : Analysis Of Skew Deck Slab Bridge By Analytical Methods

Author Name : Bikram Kesharee Patra, Rajesh Kumar, Veerendra Kumar

Synopsis :

Bridges and culverts form important parts of a rail or road or any other type of communication network and the major part of the project of the cost of the project goes into the construction of these structures. In order to cater to high speeds and more safety requirements of the traffic, modern highways are to be straight as far as possible and this has required the provision of increasing number of skew bridges. In brief the study includes the behavior of skew slab bridges with respect to support reaction and deflection of the slab under standard IRC 70R wheeled loading. The modeling of the slab is done by using both Finite element method (FEM) and Grillage method and results are compared.

Bearing Capacity Improvement In Soils Using Waste Tire Rubber Fibers

Vol.1 No.4

Year : 2013

Issue : Dec-Feb

Title : Bearing Capacity Improvement In Soils Using Waste Tire Rubber Fibers

Author Name : Sanjeev Naval, Arvind Kumar , Bansal

Synopsis :

A series of laboratory model tests has been carried out on a model strip footing to investigate the use of waste tire fiber as reinforcement to increase the bearing capacity of soil. Fiber content and depth of reinforcement at relative density 60% are considered to be the main parameters in this paper. The fiber aspect ratio of 12.5 (length = 25mm and width =2mm) was selected. The thickness of reinforcement was kept as 0.5B, 1B, 1.5B and 2B (B is the width of the footing) and four different fiber contents of 0.25%, 0.50%, 0.75% and 1.0% by weight were selected. It has been found that Bearing Capacity Ratio of soil is improved with addition of waste tire fibers at all fiber contents and thicknesses of reinforcement. A maximum value of 1.64 has been found at a fiber content of 0.75% and thickness of reinforcement 1.5B.

Soil Structure Interaction Analysis of Pipe-Rack Structure

Vol.1 No.4

Year : 2013

Issue : Dec-Feb

Title : Soil Structure Interaction Analysis of Pipe-Rack Structure

Author Name : Anand Gharad, Sonparote

Synopsis :

For the purpose of carrying different fluids to its operating units, generally a pipe rack structure having pipes of various sizes laid on it is used in an industrial refinery plant. Sudden opening or closing of pipe valves leads to water hammer effect. Also at pipe bends, this phenomenon is prevalent. A soil structure (pipe-rack) interaction is carried out. By coupling the infinite elements (H.R. Yerli, B. Temel and E.Kiral 1998) with standard finite elements, an ordinary finite element procedure is used for simulation of wave propagation in an unbounded foundation due to external forces. Example studied here indicates that the present approach can be useful for analyzing the transient response of soil-structure interaction problems.

Structural System Degradation Due to High Temperature Arising from Fire

Vol.1 No.4

Year : 2013

Issue : Dec-Feb

Title : Structural System Degradation Due to High Temperature Arising from Fire

Author Name : Jamshid Mohammadi, Jiahong (Joanne) Zuo

Synopsis :

Among major effects of high temperatures on structural materials include a dramatic change in thematerial behavior and a reduction in the load resistance capacity. In a structural system, the high temperatures from fire along with the changes occurredto the material properties and behavior may affect the system's integrity and capability to supportloads. As the fire persists in a building, structural components suffer a gradual degradation processthat may eventually lead to structural collapse. From the serviceability point of view, a building isconsidered a loss once fire spreads to a major portion of it regardless of whether structural collapseoccurs or not. However, the collapse prevention is especially important to the safety of fire fighterswho stay around or inside the building until the fire is completely contained. In this regard, animportant design consideration is how to treat the collapse issue in a design code. At the presenttime, fire protection coating remains as the only safeguard against fire in buildings. No specificguidelines exist to address design strategies to reduce the risk of collapse in buildings during fire.In an effort to clarify on design issues for buildings subject to high temperature arising from fire,this paper presents the results of an investigation into the behavior of structures subject to hightemperatures during fire. Floor systems made up of reinforced concrete slabs with or withoutintermediate beams were investigated under application of a loading that consisted of dead load andfire exposure. The effect of high temperature on material strength and behavior; creep and crackingin concrete; formation of localized failures; and structural degradation resulting from loss of stiffnesswere investigated using a nonlinear finite element analysis. The analysis simulated the loadingprocess and followed the step-by-step structural degradation of floor systems until a predeterminedcollapse criterion was reached. The results revealed a dramatic loss of structural stiffness after atemperature increase of about 400-500 ° C. The paper also describes the significance of fire loadsin structural analysis and design. Issues pertinent to design include: (1) prevention; and (2) designfor safe performance in a fire. These issues as related to a performance-based design code arereviewed and discussed.